I've been on a used and low-priced NOS tube buying spree lately. All around the 6CG7 signal tube for the TP. I've settled on the Mullard 5U4G as the rectifier so far (although the Philips GX32 keeps getting its turn at bat). I've bought, for the signal side:
RCA Clear tops
Raytheon black plates (Made in USA ones, rather rare but inexpensive)
RCA black plates for the late 50's and early 60's
Sylvania gray plates from 1957-58, with green lettering
Sylvania gray plates, from early 60's, with yellow lettering
Up until this latest push I've been most pleased with the RCA 6BQ7's and to a lesser extent the Sovtek 6N1P's. When I put the RCA Clear Tops in they sounded very bright, as NOS tubes sitting on a shelf for 40 yrs would sound. After a few days they settled into very fine sounding tubes, the bes...so far. But then, after reading about some folks liking the cheap USA-made Raytheon black plates I scored a pair for like $15, along with Emersons and the RCA black plates for similar pin money. The past two days have had the Raytheons warming up, and they are now the benchmark. The soundstage is deeper, the midranges sweeter, the highs a notch less tizzy than even before. If David/Frank's feedback on the DR's are that good, I at least know I've got a few back ups for almost no money. And some folks think the RCA black plates will do almost the same as the Raytheons, with the 1958 Sylvania green labels either a masterpiece (and find of the year) or ho-hum. Once Bob and gang leave this weekend the Sylvanias may go in the hotseats. (Problem is: Bob's latest tweeter upgrade to the Revs is an infinitesimally low rated resistor across the tweeter, solving a tweeter control issue, so my cymbals and ultra HF sonics might need to be re-evaluated with the whole cadre of tubes after this weekend. And his ZR cables will change the landscape, too. Yikes.
Oh well, that's what this hobby is all about. I can;t wait to hear how the DR's sound on the pre. I'm having Brendan send me a couple of other low cost web faves, a pair of Sylvania 5R4GYB recitifers to try in my dual mono 36.5 PS. I could end upo finding that some of these "finds" are just not right for my system, but I'll be out pennies....then again if the DR's are da bomb, those pennies will need to be carried in a very large sack!